.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" %%%LICENSE_START(VERBATIM)
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.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
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.\" Since the Linux kernel and libraries are constantly changing, this
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.\" %%%LICENSE_END
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2002-08-10 by Walter Harms (walter.harms@informatik.uni-oldenburg.de)
.TH COPYSIGN 3  2016-03-15 "GNU" "Linux Programmer's Manual"
.SH NAME
copysign, copysignf, copysignl \- copy sign of a number
.SH SYNOPSIS
.nf
.B #include <math.h>
.sp
.BI "double copysign(double " x ", double " y );
.br
.BI "float copysignf(float " x ", float " y );
.br
.BI "long double copysignl(long double " x ", long double " y );
.fi
.sp
Link with \fI\-lm\fP.
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.in
.sp
.ad l
.BR copysign (),
.BR copysignf (),
.BR copysignl ():
.RS 4
_ISOC99_SOURCE || _POSIX_C_SOURCE\ >=\ 200112L
    || /* Since glibc 2.19: */ _DEFAULT_SOURCE
    || /* Glibc versions <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.RE
.ad b
.SH DESCRIPTION
These functions return a value whose absolute value matches that of
.IR x ,
but whose sign bit matches that of
.IR y .

For example,
.I "copysign(42.0,\ \-1.0)"
and
.I "copysign(\-42.0, \-1.0)"
both return \-42.0.
.SH RETURN VALUE
On success, these functions return a value whose magnitude is taken from
.I x
and whose sign is taken from
.IR y .

If
.I x
is a NaN,
a NaN with the sign bit of
.I y
is returned.
.SH ERRORS
No errors occur.
.SH ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lbw36 lb lb
l l l.
Interface	Attribute	Value
T{
.BR copysign (),
.BR copysignf (),
.BR copysignl ()
T}	Thread safety	MT-Safe
.TE
.SH CONFORMING TO
C99, POSIX.1-2001, POSIX.1-2008.
.\" 4.3BSD.
This function is defined in IEC 559 (and the appendix with
recommended functions in IEEE 754/IEEE 854).
.SH NOTES
On architectures where the floating-point formats are not IEEE 754 compliant,
these
functions may treat a negative zero as positive.
.SH SEE ALSO
.BR signbit (3)
